1. The Field of the Invention
This invention relates to self propelled vehicles used to transport articles and personnel in locations where the vertical clearance is limited, such as in below ground mining and aircraft support operations. More particularly, the present invention relates to methods of converting normal profile vehicles to low profile self propelled vehicles and the resulting vehicles.
2. The Prior Art
Several modern industries have a need for self propelled low profile vehicles. Examples of such industries are the mining and aircraft maintenance and support industries. For example, both military and commercial aircraft require ground support vehicles which are capable of maneuvering under aircraft wings and fuselages. In the mining industry, vehicles are required to maneuver in low clearance mine roadways to transport personnel, maintenance equipment, fuel and lubricates, and other items from one location to another in the mining operation.
Low profile vehicles are generally defined as those having a maximum vertical height of eighty, and usually less than about sixty, inches or less. The vertical height of a vehicle is generally measured from the underlying road or ground surface to the highest rigid structure on the vehicle.
Not only must a low profile vehicle be able to pass under low clearances, but it must also carry payloads of anywhere in the range from hundreds to thousands of pounds reliably over rough road conditions. Thus, a low profile vehicle should be as thoroughly engineered and tested as normal profile vehicles which are mass produced by the tens of thousands.
Moreover, normal profile vehicles which are intended for use on city streets and highways are generally built so that the operator's cab is raised to the highest practical vertical height to improve visibility of the surrounding traffic from the operator's cab. Normal profile vehicles, such as those which are intended to be operated on city streets and highways generally have a vertical height in the range from eighty to one-hundred and twenty inches. Thus, it is widely recognized among those having skill in the art that normal profile vehicles do not have application in industries requiring low profile vehicles.
The general recognition in the pertinent industries that low profile vehicles are a necessity under certain conditions has caused some manufacturers to produce specialized low profile vehicles. It is the usual case that specific industries, profile vehicles are custom built for specific industries, e.g., vehicles are designed and built individually, or in quantities only in the tens, specifically for the mining or for the aircraft support industries. This is in contrast to the tens, or hundreds, of thousands of a particular chassis of a normal profile vehicle which will customarily be produced by a manufacturer.
Manufacturers of such specialized low profile vehicles include Eimco Mining Machinery International of Canada; A. L. Lee Corp. of Lester, W.V.; and Getman Corporation of Bangor, Mich.
The market for such specifically designed and custom built low profile vehicles is very limited with some manufacturers producing only a few of each model of low profile vehicle each year. Thus, each low profile vehicle is generally built on an individual basis, or in very few numbers, to fill the need of a particular customer or class of customers.
It is widely acknowledged that producing such small numbers of specifically designed low profile vehicles is inherently inefficient. Thus, the cost of each low profile vehicle is very high compared to vehicles which are mass produced and directed to a larger number of users.
Moreover, since so few low profile vehicles are built by each manufacturer, the design and fabrication of the vehicles requires that simple and readily available components, material, and fabrication techniques be used. For example, in mass produced vehicles where tens of thousands are manufactured, such as normal profile trucks, the frame, engine, drive train components, and body parts are all specifically designed and extensively tested to ensure that they work together properly and in a trouble free manner.
In contrast, low profile vehicles are designed by each manufacturer and built in small numbers from the "ground up" with no other perspective in mind but to produce the vehicle for the intended specific end use. Thus, low profile vehicle manufacturers are left to obtain components such as engines, drive trains, and brake systems from other sources where they are mass produced. The remaining components used in low profile vehicles, such as frames and body parts, must be individually fabricated by the vehicle manufacturer.
As recognized in the arts devoted to design and production of normal profile vehicles, the compatibility of vehicle components is crucial to making a vehicle perform most efficiently. Ensuring that vehicle components are compatible requires a great deal of design, engineering, and testing effort before production of the vehicle begins. Such extensive design, engineering, and testing efforts are prohibitively expensive in view of the small numbers of low profile vehicles which are manufactured. Unfortunately, the use of "high quality" and individual components does not ensure that the components will work well together.
Since the frames, bodies, and other components of prior art low profile vehicles must be designed and fabricated in small numbers, they are of simple construction and are fitted with components which are not ideally suited for use therewith. In the case of body parts, large flat pieces of sheet metal are generally attached to a simple geometric framework giving the completed low profile vehicle a "boxy" and "unfinished" appearance when compared to mass produced normal profile vehicles.
Moreover, the fact that each prior art low profile vehicle is individually designed and built causes most manufacturers to omit the design, fabrication and installation of many desirable features into their low profile vehicles. Such omitted features may include performance enhancing features such as drive train, exhaust system, and suspension, braking, and fuel system improvements.
Also omitted from prior art low profile vehicles are even basic amenities for the comfort and safety of the low profile vehicle operator such as cab environmental control, roll down windows, padded dashboard, windshield wipers, and windshield washers. In some cases, low profile vehicles do not provide the operator with any enclosed cab at all.
Further drawbacks which are evident with some prior art low profile vehicles is that the driver and steering wheel are offset from the longitudinal axis of the vehicle, in some cases by as much as 90.degree.. Thus, the low profile vehicle operator must sit and steer sideways. Still further, some manufacturers of low profile vehicles utilize a two piece articulated frame scheme which increases the cost of producing and maintaining the low profile vehicle.
Still another drawback inherent in prior art low profile vehicles is the fact that a new chassis is generally designed for each application. For example, a two person transport, a twelve person transport, and a large two ton equipment transport would each be designed from the ground up using all different components. Disadvantageously, this scheme also requires that an owner of such vehicles maintain a different complete parts inventory and trained repair technicians for each of the different vehicles.
In view of the foregoing, it would be an advance in the art to provide a low profile vehicle which includes the desirable features present in normal profile vehicles while providing the low profile vehicle at a lower cost than prior art low profile vehicles. It would be a further advance in the art to provide a method of converting normal profile vehicles for use as low profile vehicles. It would also be an advance in the art to provide a low profile vehicle conversion which allows low profile vehicles to be produced more efficiently than are prior art low profile vehicles which are designed and built in small numbers for specific end uses.